Alcohol use and risk of dementia in diverse populations

ObjectiveTo examine the causal relationship between alcohol use and dementia risk across multiple ancestry groups. DesignWe triangulated evidence from observational and univariable and multivariable Mendelian randomization. Setting and participantsCross-ancestry observational analyses were conducted in two large prospective studies: the US Million Veteran Program and UK Biobank. One- and two-sample univariable and multivariable Mendelian randomization used de novo data from a genome-wide association study in Million Veteran Program plus publicly available data. Main outcome measureAll-cause dementia. ResultsAmong 559,559 participants (aged 56-72 years old at baseline) included in observational analyses, 14,540 received developed dementia and 48,034 died during follow-up. Observational associations between alcohol and dementia were U-shaped. Non-, heavy (>40 drinks per week - hazard ratio (HR)1.41; 95% confidence interval [CI], 1.15 to 1.74]) and dependent (1.51[1.42-1.60]) drinkers were at higher dementia risk than light drinkers. In contrast, genetic analyses revealed a monotonically increasing association between alcohol dose and dementia, with no evidence supporting a protective effect of any level of drinking. A two-fold increase in genetically-predicted alcohol use disorder prevalence was associated with a 16% increase in dementia cases (IVW OR=1.16[1.03-1.30]), and a one standard deviation increase in log-transformed drinks per week was associated with a 15% increase (IVW OR=1.15[1.03-1.27]). ConclusionsAlcohol consumption has a causal role for dementia. These findings challenge a purported protective effect of moderate drinking. Reducing alcohol use could be an effective dementia prevention strategy.